<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
</head>

<style>
	body,dl,dt,dd,p{margin:0;padding:0;}
	body{font-family:Tahoma;font-size:12px;}
	label,input,a{vertical-align:middle;}
	label{padding:0 10px 0 5px;}
	a{color:#09f;text-decoration:none;}
	a:hover{color:red;}
	dl{width:120px;margin:10px auto;padding:10px 5px;border:1px solid #666;border-radius:5px;background:#fafafa;}
	dt{padding-bottom:10px;border-bottom:1px solid #666;}
	dt label{font-weight:700;}
	p{margin-top:10px;}
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<script>
	window.onload = function(){
		var oA = document.getElementsByTagName("a")[0];
		var oInput = document.getElementsByTagName("input");
		var oLabel = document.getElementsByTagName("label")[0]; 
		
		var isCheckAll = function(){
			for(var i = 1 , n=0;i<oInput.length;i++){
				oInput[i].checked && n++;
			}
			oInput[0].checked = n == oInput.length - 1;
			oLabel.innerHTML = oInput[0].checked ? "全不选" : "全选";
		}

		//全选/全不选
		oInput[0].onclick = function(){
			for(var i = 1;i < oInput.length; i++){
				oInput[i].checked = this.checked;
			}
			isCheckAll();
		};

		//反选
		oA.onclick = function(){
			for(var i = 1;i < oInput.length; i++){
				oInput[i].checked = !oInput[i].checked; 
			}
			isCheckAll();
		};

		//根据复选个数更新全选框状态
		for(var i = 1; i < oInput.length;i++){
			oInput[i].onclick = function(){
				isCheckAll();
			}
		}
	}
</script>

<body>

<dl>
    <dt><input type="checkbox" id="checkAll" /><label>全选</label><a href="javascript:;">反选</a></dt>
    <dd>
        <p><input type="checkbox" name="item" /><label>选项（一）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（二）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（三）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（四）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（五）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（六）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（七）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（八）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（九）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（十）</label></p>
    </dd>    
</dl>
<center>1、切换全选/全不选文字；2、根据选中个数更新全选框状态；</center>

	
</body>
</html>